1. Field of the Invention
The present invention relates to a roller stocker and a method for fabricating a liquid crystal display (LCD) device and, more particularly, to roll stocker capable of corresponding to various models of mother substrates and keeping a sufficient number of rubbing rolls for securing a margin for roll operation, and a fabrication method of a liquid crystal display (LCD) device using the same.
2. Description of the Related Art
As demand for information displays and for portable (mobile) information devices grows, research and commercialization of light and thin flat panel displays (“FPD”) has increased. Flat panel displays are increasingly replacing the Cathode Ray Tube (“CRT”), as the most common display device.
The liquid crystal display (“LCD”) device is a FPD device to display images using the optical anisotropy of liquid crystal. LCD devices exhibit excellent resolution and color and picture quality, so it is widely applied for notebook computers or desktop monitors, and the like.
In the LCD device, a data signal containing image information is separately supplied to liquid crystal cells arranged in a matrix form, and light transmittance of the liquid crystal cells is controlled to display the desired image.
FIG. 1 is an exploded perspective view illustrating the structure of a LCD device.
As illustrated in FIG. 1, the LCD device includes a color filter substrate 5, namely, a first substrate, an array substrate 10, namely, a second substrate, and a liquid crystal layer 40 formed between the color filter substrate 5 and the array substrate 10.
The color filter substrate 5 includes a color filter (C) comprising sub-color filters 7 for implementing red (R), green (G) and blue (B) color, a black matrix 6 for discriminating the sub-color filters 7 and blocking light transmitting through the liquid crystal layer 40, and a transparent common electrode 8 for applying a voltage to the liquid crystal layer 40.
The array substrate 10 includes gate lines 16 and data lines 17 which are arranged on the substrate 10 and define pixel regions (P). A thin film transistor (TFT), a switching element, is formed at respective crossings of the gate lines 16 and the data lines 17, and a pixel electrode 18 is formed at each pixel region (P).
The pixel region (P) is a sub-pixel corresponding to one sub-color filter 7 of the color filter substrate 5, and a color image is obtained by combining three types of red, green and blue sub-color filters 7. Namely, the three red, green and blue sub-pixels form one pixel, and the TFTs are connected with the blue, green and blue sub-pixels.
An alignment film (not illustrated) for aligning liquid crystal molecules of the liquid crystal layer 40 is formed on the color filter substrate 5 and the array substrate 10.
FIG. 2 illustrates a method for forming an alignment film using a roll printing method.
As illustrated, generally, an alignment film is formed using a printing method using a plurality of rolls. Namely, an alignment solution 24 supplied between a cylindrical anylox roll 22 and a cylindrical doctor roll 23 is uniformly coated entirely on the anylox roll 22 as the anylox roll 22 and the doctor roll 23 are rotated. In this case, the alignment solution 24 is supplied by a dispenser 1 in an injector type.
The anylox roll 22 is rotated in contact with a printing roll 24 having a rubber plate 25 attached on a certain region of its surface, and the alignment solution 24 on the anylox roll 22 is transferred to the rubber plate 25. The rubber plate 25 corresponds to a substrate 26 on which the alignment solution 24 is to be coated, and has a master pattern to allow the alignment film to be selectively printed on the substrate 26.
As a printing table 27 with the substrate 26 loaded thereon is moved in contact with the printing roll 24, the alignment solution 24 which has been transferred to the rubber plate 25 is re-transferred onto the substrate 26 to thereby form an alignment film.
Next, with the alignment film formed on the substrate, the alignment film is rubbed to arrange liquid crystals in a certain direction to form valleys in a certain direction.
FIG. 3 is a perspective view illustrating a rubbing process.
As illustrated, the alignment film 21 is rubbed to form the recesses 36 on the surface thereof. The rubbing process refers to rubbing the surface of the alignment film 21 in a certain direction using a roller 30 with a rubbing cloth 35 wound thereon.
When the surface of the alignment film 21 is rubbed, it has fine recesses 36.
As the rubbing cloth 35, a soft cloth is used, and rubbing equipment including the roller 30 is relatively simple. The basic part for setting conditions for the rubbing process is setting a rubbing condition with a suitable strength and applying a uniform rubbing strength on a large area.
If the rubbing is not uniformly performed, an alignment degree of liquid crystal molecules is not spatially uniform, causing a defect that optical characteristics are different at a certain portion of the panel.
In addition, since the physical units such as the rolls are used in the rubbing process, management of the rolls is important with respect to stability of processes. Accordingly, it is important to secure the sufficient number of rubbing rolls to obtain a margin in operating rolls. However, there is no means for storing the rubbing rolls, and the rubbing rolls are kept standing in a vertical direction, limiting to operation of rolls. In addition, as the size of a mother substrate for fabricating a liquid crystal display panel is increased, the rubbing roll is lengthened, so there is a limitation to keep the rubbing roll in a standing state in a limited clean room.
In addition, since the rubbing rolls are kept in a fixed state, eccentricity of the rubbing roll is deviated. The eccentric of the rubbing roll is critical factor for managing a rubbing process together with a state of a rubbing cloth.
Moreover, since the rubbing rolls are kept in the opened state, the rubbing cloth is inevitably contaminated by external particles, to cause damage to the surface of the liquid crystal display panel.